| There are several key characteristics to look for when evaluating the
water efficiency of a lawn sprinkler system.
Matched-Precipitation Rate Sprinkler Heads
All sprinkler heads on a given circuit should be the same type (e.g.
rotors, pop-up spray, etc.) and have matched precipitation rate (in
inches per hour). Heads with differing precipitation rates have widely
varying operating times, which can lead to the over-watering of one area
in order to sufficiently water another.
Head-to-Head Coverage
Turf pop-up sprinkler systems are designed to operate with
head-to-head coverage, where the spray from one sprinkler head reaches
to the next, resulting in necessary overlap. Precipitation rates are
based on the assumption of overlap. Places where the sprinkler's spray
pattern does not overlap are likely not getting sufficient water and may
develop brown dry spots. These spots indicate the system has low
"uniformity" of coverage (please see Information Sheet
regarding "Distribution Uniformity"). To compensate, one has
to run the sprinklers for longer times to get adequate water to the dry
spots, while the rest of the lawn is getting over-watered.
Precipitation Rate That Does Not Exceed the Soil's
Infiltration Rate
Based upon soil characteristics, water will soak into the ground at
differing rates. Sandy soils have high (fast) infiltration rates, while
clay soils have low (slow) infiltration rates. If the precipitation rate
of the sprinkler heads exceeds the soil's infiltration rate, then runoff
and erosion occur (especially on slopes). On flat ground, this will also
lead to puddling.
If your sprinklers' precipitation rate exceeds the infiltration rate,
lower precipitation rate heads can be installed, or you can shorten your
watering times and use multiple start times (e.g. 3 start times at 5
minutes each at 1-hour intervals instead of 15 minutes all at once) to
allow the water to soak into the soil.
Appropriate Water Pressure
Each sprinkler head is designed to operate within a certain range of
pressure, typically around 40 to 50 pounds per square inch (PSI). When
water pressure is too low, the sprinkler head will emit large drops and
likely will not produce the proper spray pattern or a radius that
reaches to the next head. If pressure is too high, the head will produce
a fine mist, which leads to water loss due to evaporation and
"fly-away" in even light winds. In addition, high pressure can
lead to over spray and a distorted spray pattern, along with many other
problems (see "Pressure Reducing Valves" Information Sheet).
Clean, Even Spray Pattern
If the spray pattern of a head is distorted, browns spots may develop
on the lawn. This may be caused by blockage in the screen or in the
nozzle itself, and the head may need to be cleaned (please refer to
"Irrigation Component Maintenance"). If this does not fix the
problem, the nozzle may be worn and needs to be replaced.
No Low Head Drainage
If the irrigation circuit has some sprinkler heads that are lower
than the rest, the water remaining in the pipes after an irrigation
cycle will tend to drain from those heads each time the circuit is shut
off. In-line check valves or sprinkler heads with in-head check valves
should be installed to prevent water waste.
No Over spray
There should be no wasteful over spray onto sidewalk, patio, driveway
or street. If there is over spray, replace the nozzle with another with
the appropriate spray pattern (e.g. 180° instead of 360°) or relocate
the sprinkler head.
No Obstructions
Make sure that the spray from the head is not obstructed by
vegetation or other objects. Trim back vegetation or raise the sprinkler
heads as needed. This will increase the system's uniformity of coverage.
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